The N-methyl-D-aspartate receptor (NMDAR) is a ligand-gated ion channel protein whose function as a logic gate lies at the heart of the molecular processes of memory formation. At resting membrane potentials the presence of the glutamate ligand alone is insufficient to open the channel because its pore is blocked by Mg2+. Depolarization of the neuron removes the blockade, permitting calcium flow that initiates a strengthening of the synapse and memory formation. Excessive calcium flow through the NMDAR is believed to underlie neurodegeneration in ischemia, stroke, and several neurological diseases. Drug treatments must be able to tweak this essential protein's function back to normal. The development of such drugs requires a detailed understanding of the subtleties of the NMDAR. The NMDAR blockade site is unusual in that it is hydrophobic, rather than highly negatively charged, like most Mg2+-binding sites. We hope to dissect the Mg2+ blockade using a series of subtle and dramatic alterations to the protein structure through the site-specific incorporation of unnatural amino acids. We will functionally assay these chemical perturbations of the steric and electronic interactions with the Mg2+ cation through electrophysiology. [unreadable] [unreadable]